Cleveland Clinic Journal of MedicineLow Back Pain: Spondylitis?

Practical Insights for Diagnosing Osteitis Condensans Ilii

A 37-year-old woman presented to the rheumatology clinic with worsening low back pain, initially noticed during her pregnancy with twins. Clinical evaluation and imaging confirmed a diagnosis of osteitis condensans ilii (OCI), a benign condition often mistaken for more serious inflammatory disorders. This article provides a clinical picture into the patient’s presentation, diagnostic process, and differential considerations, providing valuable insights for practitioners managing similar cases.

Key Points:

• Patient Background:
  • 37-year-old female with low back pain worsening over 18 months.
  • Pain noted during pregnancy with twins, exacerbated by long hours and heavy lifting.
  • Pain relief with nonsteroidal anti-inflammatory drugs (NSAIDs).
  • No morning stiffness, nocturnal awakening, or difficulties in daily activities.
  • No history of enthesitis, dactylitis, or inflammatory eye disease.
• Clinical History:
  • Previous episode of colitis with notable computed tomography (CT) findings of colitis and abnormal sacroiliac joints (bilateral subchondral sclerosis).
  • Unremarkable colonoscopy performed one month later.
• Physical Examination:
  • Normal peripheral joints and spine range of motion.
  • No sacroiliac joint tenderness; negative FABER test.
  • Normal eye examination.
• Imaging Findings:
  • CT: Bilateral subchondral sclerosis on iliac sides, consistent with osteitis condensans ilii (OCI).
  • Radiography: Dense bilateral subchondral sclerosis, triangular-shaped sclerosis typical of OCI.
• Osteitis Condensans Ilii (OCI):
  • Benign, noninflammatory cause of axial low back pain.
  • Common in multiparous females, mean age 35.
  • Potential mechanisms: vascular compression, ischemia, mechanical laxity, and sacroiliac joint overload during pregnancy.
  • Symptoms: intermittent axial low back pain, occasional hip area pain, worse during or post pregnancy.
  • Imaging: bilateral triangular subchondral sclerosis, absence of erosions and ankylosis.
• Differential Diagnosis:
  • Sacroiliitis from infection, ankylosing spondylitis, psoriatic arthritis, osteoarthritis.
  • Key diagnostic features: inflammatory back pain, enthesitis, dactylitis, peripheral arthritis, extra-articular manifestations, family history of spondyloarthritis.
  • Imaging for sacroiliitis: bilateral symmetric erosions, sclerosis, ankylosis in ankylosing spondylitis.
• Management:
  • Conservative treatment with physical therapy and analgesics.
  • OCI typically resolves over years.

Although the underlying cause is unknown, it is thought that mechanical tension and imbalance across the sacroiliac joints are to blame for OCI, which leads to a long-lasting stress reaction. This theory is supported because it most frequently affects postpartum females. (Cureus)

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